There are many examples of electronic weighing apparatus or scales in the past. In some instances, it has been necessary to provide such weighing apparatus with multiple weighing points such that the weight of a load can be measured at several locations. For example, a race car needs to be balanced so that the weight on each wheel, on each end, on each side, and on each diagonal are substantially equivalent or some particular percentage of the total weight. These numbers may change and depend on a particular setup for a track. Such weighing systems, therefore, comprise a plurality of weighing pads upon which a wheel of a race vehicle is situated so that the weights for these individual locations of the load can be determined.
Previously, the multiple weighing pads of these systems have been hardwired or physically connected by detachable wires to the control unit used to interface with an operator. These hardwired systems lack flexibility and are difficult to use because the wires must be connected to the central control before weight readings can be taken. The wires can become tangled or broken and, when detachable, tend to be lost. The physical length and connections of the wires tend to limit the positioning of the central control when taking the weight measurements. This can be detrimental in situations that occur in garages and races where there may be limited access because of other equipment or personnel at that position. Further, many times the wires of electronic weighing apparatus serve as pickups for radio frequency interference which is particularly prevalent around automobiles and electronic equipment used in garage and racing locals. What is needed is a wireless weighing system including a means for the short range communication of weight information which is free from interference and can be easily implemented for an automotive racing environment.
One of the more popular communications systems for the transmission of information over short ranges is an infra-red communications system which uses optical radiation in the infra-red band as the transmission media. It is known that such systems can transmit either analog or digital information. Infra-red communications systems have several inherent advantages in that they do not generate radio frequency interference which might interfere with other electronic devices and, more importantly, infra-red receivers are virtually unaffected by radio frequency interference produced by the other devices.
One such infra-red transmission system is shown in U.S. Pat. No. 4,151,407 issued to McBride et al. McBride et al. is used for such applications as a portable transmitter which transmits infra-red information from a plurality of sensors or medical electrodes attached to a patient to a remote monitor. Additionally, a portable hand-held digital transmitter is utilized for video game control and on/off channel selection for television using infra-red energy transmission.
While the reference to McBride et al. illustrates a system where several multiplexed elements can be separated by frequency channels, the system does not disclose the manner of differentiating between a number of remote units which use digital codes. Such digital codes are much easier for modern microprocessor controls to generate and frequency modulators and demodulators can be eliminated from such systems.
Moreover, the previous systems do not teach a wireless system which can operate in high levels of ambient sunlight or other optical radiation sources with the possibly interfering sources at variable distances from the communications system. Such is the environment for a racing vehicle where a wireless weighing system would be used.